1. Field of the Invention
The present invention relates to hermetically sealed relays, and is adapted to vacuum or gas-filled relay technology with or without a latching capability.
2. Description of the Prior Art
Vacuum type and other sealed relays of the general class and performing the general functions provided by the combination of the present invention are known. U.S. Pat. No. 3,576,066 illustrates and describes such a relay as known in the prior art, with particular emphasis on processes useful in its manufacture.
Although devices of the general type are usually thought of as vacuum relays, they can be constructed as gas-filled switching devices, if desired.
Prior art devices of the type to which the present invention applies generally comprise two separately manufactured sub-assemblies prior to final assembly. One of these sub-assemblies is the hermetically sealed switch assembly itself, and the other is the actuator assembly. In the aforementioned U.S. Pat. No. 3,576,066, the first of these sub-assemblies is typically illustrated in FIG. 2, and the second in FIG. 5.
Although the present invention is not confined to the use of stacked ceramic cylinders forming the evacuated switch enclosure, that type of construction is well known in the prior art and affords significant manufacturing advantages vis-a-vis, blown-glass bulb enclosures or the like.
Prior art actuators of the required type have taken several basic functional forms, including those which provide latching in first and a second controlled positions by mechanical means and those providing magnetic hold in first or second positions to achieve a similar latching effect. These prior art actuator arrangements have usually involved lash or lost motion. Inherently, such actuators have also operated against discrete internal limits, i.e., against their own internal stops, and it therefore has been necessary to very carefully control the switch gap in the mating vacuum switch part so that the switch contacts in one or both directions will be effected with some residual force. Once the vacuum switch enclosure is fully assembled and sealed, it is not possible from a practical point of view to adjust the switch gap (i.e., the spacing between the two switch positions), and if the actuator does not provide an appropriate "overtravel" to absorb at least a portion of the switch contacts at the alternate positions, the manufacturing reject rate is likely to be high and the life of the assembly and vacuum brazing tools and fixtures quite limited.
In the prior art actuators of the type, the overall performance characteristics cannot be appropriately evaluated or production tested until after final assembly to the vacuum switch housing. Therefore, previously undetected dirt or foreign matter in the actuator may cause its rejection along with that of the switch enclosure, since the prior art actuators are not readily opened for cleaning or inspection.
Where the actuator operates against a definite stop within itself in each of two positions, any effort to relieve its own tolerance problems can result in loose parts. The same may be said of the switch assembly, per se.
Thus, the prior art arrangements in which both the switch assembly and the driving actuator operate against their own definite internal stops gives rise to manufacturing problems, particularly in respect to tolerances.
The manner in which the present invention deals with the problems of the prior art to produce a novel and improved overall device will be evident as the description proceeds.